能谱CT结合低剂量碘对比剂个体化方案成像在颈动脉CT血管成像中的价值

Clinical application of gemstone spectral imaging associated with patient-based low dose of contrast medium protocol for carotid CT angiography

目的探讨能谱cT结合低剂量碘对比剂个体化方案成像在颈动脉CTA中的应用价值。方法前瞻性收集临床疑诊为颈动脉狭窄或斑块需行颈动脉CTA检查的患者120例，按照数字表法随机分为常规组和低剂量组行颈动脉CTA检查，每组各60例。2组均采用对比剂个体化方案，按照公式计算对比剂总量，对比剂总量=（扫描延迟时间-5s）×注射流率。常规组扫描参数为管电压120kVp，注射流率5ml／s，图像进行滤波反投影重组；低剂量组采用能谱单能量扫描模式，管电压140、80kVp瞬时（0．5ms）切换，注射流率3ml／s，采用50％自适应统计迭代重组方法重组出单光子60keV图像。对2组图像进行客观评价和主观评分，客观评价指标包括颈动脉CT值、对比噪声比（CNR）及信噪比（snr），并记录对比剂总量和辐射剂量（包括容积CT剂量指数、剂量长度乘积和有效剂量）。两组间图像质量主观评分和辐射剂量的比较采用Mann—Whitneyu非参数检验，图像质量客观评分和对比剂总量的比较采用独立样本t检验。结果常规组颈动脉CT值、背景噪声、SNR、CNR、主观评分、对比剂总量、容积CT剂量指数、剂量长度乘积和有效剂量分别为（363±56）HU、（13±4）HU、30±10、38±13、3．0分、（69±13）ml、13．61mGy、527mGy·（31／1和3．11mSv，低剂量组上述指标分别为（378±69）HU、（9±4）HU、48±19、62±24、2：0分、（49±7）ml、12．72mGy、478mGy·cm和2．82mSv。2组图像间的颈动脉CT值和主观评分差异无统计学意义（P均〉0．05），背景噪声、SNR、CNR、对比剂总量、容积CT剂量指数、剂量长度乘积和有效剂量间的差异均有统计学意义（P均〈0．05）。结论采用能谱CT结合低剂量碘对比剂个体化方案行颈动脉CTA，在取得良好图像质量的同时，可以减少对比剂用量，降低辐射剂量。

Objective To investigate the clinical value of gemstone spectral imaging （GSI） associated with patient-based low dose of contrast medium protocol in carotid CTA. Methods One hundred and twenty patients who were suspected with stenotic carotid artery or carotid plaque were prospectively enrolled in the study. All of them were divide into two groups by random number table. Group A （routine group）： 60 were scanned with 120 kVp after the administration of moderate-concentration CM（320 mg/ml） with 5 ml/s injection velocity, Group B （low dose group）： 60 were scanned with GSI which was reconstructed using 50 % ASiR after the administration of the same CM with 3 ml/s injection velocity. The contrast dose ]（test bolus peak time ＋ 2 s - 5 s）~ injection velocity] was calculated. Images of the two groups were compared in terms of arterial attenuation, signal-noise-ratio （SNR）, contrast-to-noise ratio （CNR）, and subjective image quality （IQ） score. The value of CT dose index volume （CTDIvol）, dose length product （DLP） and effective dose （ED） was recorded, respectively. Data were analyzed by using independent samples t test or Mann-Whitney U test. Results The mean attenuation, noise, SNR, CNR, subjective image quality score, contrast dose, CTDIvol, DLP and ED of routine group was （363 ± 56）HU, （13 ± 4）HU, 30 ± 10, 38±13, 3.0 score, （69 ± 13） ml, 13.61 mGy,527 mGy. cm and 3.11 mSv, respectively. The above variables of low-dose-group was （378 ± 69） HU, （9 ± 4）HU, 48 ± 19, 62 ±24, 2.0 score, （49 ± 7）ml, 12.72 mGy, 478 mGycm and 2.82 mSv, respectively. The mean attenuation and subjective IQ score of carotid artery had no significant differences statistically between two groups （P〉0.05）, respectively. The noise, SNR, CNR, contrast dose, CTDIvol, DLP and ED had significant differences statistically between two groups （P〈 0.05）, respectively. Coneluslon Compared with 120 kVp protocol, the use of GSI associated with patient-based low dose of contrast medium protocol in carotid CTA could provide equivalent image quality and higher SNR and CNR of carotid artery with a smaller amount of iodine and a lower radiation dose.